Hamelberg



2 Sheets-Sheet 1 INVENTOR. AUGUST HAMELBERG A. HAMELBERG ELECTRIC CONTROL DEVICES March 10, 1964 Filed Aug. 28, 1961 FIG. I

March 10, 1964 A. HAMELBERG 3,124,775

ELECTRIC CONTROL DEVICES Filed Aug. 28, 1961 z Sheets-Sheet 2 FIG. 3 FIG. 4

INVENTOR. AUGUST HAMEIBERG United States Patent 3,124,775 ELECTRIC CONTROL DEVICES August Hamelberg, Minneapolis, Minn., assiguor to Mmneapolis-Honeywell Regulator Company, Mmneapolls, Minn, a corporation of Delaware Filed Aug. 28, 1961, Ser. No. 134,508 16 Claims. (Cl. 338163) This invention relates to the field of electrical instruments, and more particularly to variable resistors for use as trimmers in connection with hermetically sealed electrical equipment. Such variable resistors are by their very nature more susceptible to failure than fixed components. Moreover, it is necessary to assemble them to the hermetically sealed electrical equipment in such a Way that the hermetic seal is maintained. This is most ad vantageously done by soldering, which results in temperatures higher than the nonmetallic insulation and the delicate resistance element can sustain without damage. Furthermore, it is frequently desirable to be able to replace the resistance element or change it to one having a different resistance value without opening the hermetically sealed units of which the trimmers form a part.

The present invention, therefore, has as objects to provide an improved variable resistor, to provide improved means for incorporating a variable resistor into a circuit otherwise hermetically sealed, to provide a variable resistor, the metallic housing of which, not containing at that time any parts susceptible of damage by high temperatures, can be soldered to a container to form a hermetic seal between the housing and the container, to provide a variable resistor which can easily be disassembled to replace the resistance element either in case of failure or because a change in other components of the system requires a different resistance value, without the necessity of unsoldem'ng and resoldering any electrical connections, and to provide a novel sealing means for variable resistors of the screw driver adjusted type which simultaneously locks the resistor frictionally against inadvertent adjustment.

Various other objects, advantages, and features of novelty' not individually enumerated above which characterize my invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and objects attained by its use, reference should be had to the subjoined drawing, which forms a further part hereof, and to the accompanying descriptive matter, in which I have illustrated and described a preferred embodiment of my invention.

In the drawing, FIGURE 1 is a plan view of a variable resistor according to the invention, FIGURE 2 is a generally sectional view taken along the line 2-2 of FIGURE 1, FIGURE 3 is a view similar to- FIGURE 1 with certain parts removed to more clearly show other parts, FIGURE 4 is a fragmentary longitudinal section taken generally along the line 44 of FIGURE 3, and FIGURES 5 and 6 show details of a component of the invention.

The invention is shown to comprise a metallic housing 10 which may advantageously be provided with an external shoulder 11 for soldering into the container of a hermetically sealed unit. Housing 10 is cup-shaped, with a wall 12 having a re-entrant rim 13 and a bottom comprising a header 15- which has a metallic rim 14- for soldering to wall 12, and through the insulating portion 16 of which pass a plurality of contact pins 17, '20, and 21. It will be apparent that when wall 12 of housing 10 is soldered to rim 14 and shoulder 11 is soldered into a suitable container, with rim 1'3 directed outwardly, the container may be hermetically sealed. A spacing washer 2 22 is provided to prevent solder from running over the inner surface of header 15.

A resilient contact member 23 is spot welded or otherwise permanently secured to the inner end of pin 17 in such a manner as to yield to [force acting toward header 15.

Housinfi 10 contains a resistance wafer 24, a wiper wafer 25, an O-r-ing 26, and a drive member 27, all held in the housing by a bowed snap ring 30. Resistance Wafer 24 includes a base 3-1 of insulating material, having clearance openings to pass pins 20 and 21 and an elongated clearance opening 32 to pass pin 17 and contact member 23, and an annular resistance element 33, the ends of which are fastened to a pair of spring contacts 34 and 35 riveted to base 31 at 36 and 37 and arranged to resiliently engage pins '20 and 21, all respectively, to make electrical contact therewith. Wafer 24 is prevented from rotating in housing 10 by engagement of pins 20 and 21 with their clearance openings, but may be removed from the housing by simple axial displacement.

Wiper Wafer 25 comprises a shallow inverted cupshaped plastic element 40, having an inwardly extending rim 41 which rides on base 31 and an outwardly extending tongue 42 by which it may be rotated, and a disk 43 of electrically conducting material cemented Within element 40' and having an inwardly extending resilient wiper arm 44.

Drive member 27 includes a groove 45 to receive tongue 42, a shouldered tapering portion 46 to engage and radially and inwardly compress 'O-ring 26, and a screw driver slot 47. Snap ring 30 engages the outer surface of drive member 27 and the inner surface of rim 13 to maintain the unit assembled.

Suitable lubrication is applied to members 25, 26, and 27 to permit easy assembly of the unit and smooth rotation of wiper wafer 25 in housing 10. Drive member 27 so dimensioned that C-ring 26 is compressed to the point where it not only makes a good seal against entry of foreign matter into the unit, but also acts as a fricrtion lock to maintain wiper wafer 25 in any position to which it maybe rotated. v

If it becomes necessary to replace a defective resistance element 33, or substitute one having a different resistance, it is only necessary to release snap ring 30 and remove drive member 27, O-ring 26, and wiper wafer 25. Resistance wafer 24 can then be Lifted out of housing 10 and a replacement substituted, after which the unit can as easily be reassembled. This can all be done without in any way disturbing the hermetic sealing of the circuit of which the variable resistor is a part.

Numerous objects and advantages of my invention have been set forth in the foregoing description, together with details of the structure and function of the invention, and the novel features thereof are pointed out in the appended claims. The disclosure, however, is illustrative only, and I may make changes in detail, especially in matters of shape, size, and arrangement of parts, within the principle of the invention, to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

I claim as my invention:

1. In combination: a housing having a bottom of insulating material with several electrically conducting pins passing therethrough in hermetically sealed relation to project inwardly therefrom; a resilient contact member carried within said housing by one of said pins; a resistance wafer insertable in and removable from said housing including an insulating base having a first clearance opening for said one of said pins and said contact member and further clearance openings for further pins, a circular resistance element mounted on said base, and spring contact means secured to said base in alignment with said further openings for engagement by said further pins and electrically connected to the ends of said resistance element; a wiper wafer independently insertable in and removable from said housing including an electrically conductive disk, means mounting said disk for rotation in its own' plane adjacent to said resistance wafer in electrical engagement with said contact member, and a Wiper arm extending from said disk to engage said element; and means resiliently maintaining and sealing said wiper Wafer in said housing for frictionally resisted rotation with respect to said resistance wafer.

2. In combination: a cup-shaped housing having a reentrant rim and a bottom of insulating material with several electrically conducting pins passing therethrough in hermetically sealed relation to project inwardly therefrom; a resilient contact member carried within said housing on one of said pins; a resistance wafer in said housing including an insulating base having a first clearance opening for said one of said pins and said contact member and further clearance openings for further pins, a substantially circular resistance element mounted on said base, and spring contact means secured on said base in alignment with said further openings and electrically connected to the ends of said resistance element, the thickness of said assembly being substantially the same as the extent of inward projection of said pins from said bottom; a wiper wafer including an electrically conducting disk, means mounting said disk for rotation in its own plane adjacent to said resistance assembly in electrical engagement with said contact member, a wiper arm extending from said disk to engage said element, and torque transmitting means for causing said rotation of said disk; an annular resilient member in said housing above said wiper wafer; a drive member in said housing above said resilient member including means cooperating with said torque transmitting means to cause said rotation of said disk, lneans cooperating with said resilient member to seal said housing and frictionally resist rotation of said drive member, and means for applying torque to said drive member; and removable means cooperating with said drive member and said re-entrant rim to maintain said drive member in cooperation with said resilient member and said torque transmitting means.

3. In combination: a circular, drivable member mounted in a circular housing for rotation such that a plane surface thereof rotates in its own plane with no substantial component of motion normal thereto; an annular resilient member engaging said surface and the inside of said housing; a drive member engaging said drivable member in driving relation and having a tapering surface for engaging said resilient member; and means acting between said housing and said drive member in a direction substantially. normal to said plane, to maintain said tapering surface in outwardly deforming engagement with said resilient member.

4. In combination: a base; an annular resistance member mounted on said base; a wiper member including a disk mounted adjacent said base, means engaging the circumference of said disc to guide it for rotation in its own plane about a center coaxial with said annular resistance member, and a wiper arm extending from said disk for continuous electrical engagement with said resistance member; and resilient contact means extending through saidbase for continuous electrical engagement with said disk.

5. In combination: a cup-shaped housing having a reentrant rim and a bottom of insulating material; a resistance wafer, including a resistance element, element removably receivable in said housing, means extending through said bottom for automatically making electricalc'onnection to said element; a wiper assembly removably receivable in said housing for rotation with respect to said element in electrical engagement therewith; means extending through said bottom and said resistance wafer electrically g g said wiper assembly throughout the rotation thereof; and means, including an annular resilient member, cooperating with said rim to maintain and seal said element and said assembly in said housing, and to cause frictionally resisted relative rotation between said member and said assembly.

6. In a variable resistor: a water of electrically insulating material having a pair of apertures therethrough; an annular resistance member mounted on a first face of said wafer; a pair of spring contacts electrically connected to the ends of said member; and means mounting said contacts on said first face of said wafer to resiliently overlie said apertures.

7. In a variable resistor: a wafer of electrically insulating material having a first face recessed to provide a central cavity and a surrounding rim; wiper means including a disc of resilient electrically conducting material peripherally deformed to comprise an integral resilient finger extending out of the plane of the disc; and means mounting said wiper means in the cavity in said first fac With said finger projecting beyond said rim.

8. In a variable resistor, in combinationi a first wafer of electrically insulating material having a pair of apertures extending therethrough, an annular resistance member mounted on a first face thereof, a pair of spring contacts electrically connected to the ends of said resistance member, and means mounting said spring contacts on said first face of said wafer to resiliently overlie said pair of apertures; a second, circular wafer of electrically insulating material having a first face recessed to provide a central cavity and a surrounding rim, wiper means including a disc of resilient electrically conducting material peripherally deformed to comprise an integral resilient finger extending out of the plane of the disc, and means mounting said wiper means in said cavity with said finger projecting beyond said rim; means mounting said wafers with said first faces in contact, so that said finger electrically engages said resistance member, including means engaging the circumference of said second wafer to determine an axis of rotation therefor; and means for applying torque to said second wafer to cause it to rotate about said axis.

9. In a variable resistor, in combination: a first wafer of electrically insulating material having a pair of apertures and a further aperture extending therethrough, an annular resistance member mounted on a first face thereof, a pair of spring contacts electrically connected to the ends of said resistance member, and means mounting said spring contacts on said first face of said wafer to resiliently o'verlie said pair of apertures; a second, circular wafer of electrically insulating material having a first face recessed to provide a central cavity and a surrounding rim, wiper I means including a disc of resilient electrically conducting material peripherally deformed to comprise an integral resilient finger extending out of the plane of the disc, and means mounting said wiper means in said cavity with said finger projecting beyond said rim; means mounting said wafers with said first faces in contact, so that said finger electrically engages said resistance member, including means engaging the circumference of said second wafer to determine an axis of rotation therefor; and means projecting through said further aperture in said first wafer for electrically engaging said disc.

10. In a variable resistor, in combination: a first Wafer of electrically insulating material having a pair of apertures and a further aperture extending therethrough, an annular resistance member mounted on a first face thereof, a pair of spring contacts electrically connected to the ends of said resistance member, and means mounting said disc, and means mounting said wiper means in said cavity with said finger projecting beyond said rim; means mounting said wafers with said first faces in contact, so that said finger electrically engages said resistance member, including tmeans engaging the circumference of said second wafer to determine m axis of rotation therefor; and means projecting through said first wafer for electrically engaging said spring contacts and said disc.

11. In a variable resistor: a circular wafer of electrically insulating material having a pair of apertures extending therethrough, an annular resistance member mounted in a first face thereof, a pair of spring contacts electrically connected to the ends of said member, and means mounting said spring contacts on said first face of said wafer to resiliently overlie said pair of apertures; a cup-shaped housing having a substantially flat bottom; a pair of electrically conducting pins extending through the bottom of said housing and located for alignment with said pair of apertures in said wafer, said pins projecting inwardly from said bottom for a distance at least slightly greater than the effective thickness of said wafer; and means resiliently pressing said wafer toward the bottom of said housing, to maintain contact between said pair of pins and said pair of spring contacts.

12. In a variable resistor: a circular water of electrically insulating material having a pair of apertures extending therethrough, an annular resistance member mounted on a first face thereof, a pair of spring contacts electrically connected to the ends of said member, and means mounting said spring contacts on said first face of said wafer to resiliently overlie said pair of apertures; a cup-shaped housing having a substantially fiat bottom and a substantially cylindrical wall; a pair of electrically conducting pins extending through the bottom of said housing and located for alignment with said pair of apertures in said wafer, said pins projecting inwardly from said bottom for a distance at least slightly greater than the effective thickness of said wafer; means including a second wafer rotatably engaging a portion of said first wafer and urging it into contact with said bottom so that said pins make good electrical connection with said spring contacts; and wiper means carried by the last named means for electrically engaging said resistance member at different points along the periphery thereof as said second wafer is rotated.

13. In a variable resistor: a circular wafer of electrically insulating material having a pair of apertures and a further aperture extending therethrough, an annular resistance member mounted on a first face thereof, a pair of spring contacts electrically connected to the ends of said member, and means mounting said spring contacts on said first face of said wafer to resiliently overlie said pair of apertures; a cup-shaped housing having a substantially flat bottom and a substantially cylindrical wall; a pair of electrically conducting pins extending through the bottom of said housing and located for alignment with said pair of apertures in said wafer, said pins projecting inwardly from said bottom for a distance at least slightly greater than the eifective thickness of said wafer; means including a second wafer rotatably engaging a portion of said first wafer and urging it into contact with said bottom so that said pins make good electrical connection with said spring contacts; wiper means carried by the last named means for electrically engaging said resistance member at differcut points along the periphery thereof as said second wafer is rotated; and means including a further electrically conductive pin extending through said bottom and said further aperture for resiliently engaging said wiper means.

14. In combination: a cup-shaped housing having an electrically insulating bottom and a substantially cylindrical wall; a removable resistance wafer in said housing having an aperture extending therethrough; a removable wiper wafer rotatable in said housing in at least partial contact with said resistance wafer and including a metallic disc having an integral finger extending therefrom toward said resistance wafer; an electrically conducting pin extending through the bottom of said housing and located for alignment with and projecting through said aperture; and resilient means carried by said pin for continuously engaging said disc as said wiper wafer rotates.

15. In combination: a cup-shaped housing having an electrically insulating bottom and a cylindrical wall with an external shoulder adapted to be hermetically sealed in an opening in the wall of a container so that the housing is for the most part within the wall of the container; conducting pins extending through said bottom and projecting inwardly into the housing; an apertured resistance wafer insertable in and removable from said housing, including a resistance member and spring contacts connected thereto and mounted on said wafer for engaging certain of said pins to make electrical connections therewith, said pins thereafter preventing rotation of said wafer in said housing; a wiper wafer insertable in and removable from said housing, including a portion adapted to contact said resistance wafer to maintain said spring contacts in engagement with said certain pins, a wiper in the form of an electrically conducting disc having an in tegral finger extending therefrom for engagement with said resistance member, and means for causing rotation of said wiper wafer in said housing; resilient means carried by another of said pins and received in the aperture in said resistance wafer for continuously engaging said disc as said wiper wafer is rotated; and means resiliently maintaining said wafers in engagement in said housing.

16. A modular variable resistor comprising, in com bination: a housing including self supporting electrically conducting members passing through and insulated from the base thereof and projecting inwardly therefrom; a resistance module insertable into said housing to lie ad jacent the bottom thereof, and having apertures for passage of said members and spring contacts means for engaging at least certain of said members; a Wiper module insertable into said housing to lie adjacent said resistance module, including means for engaging one of said contact members; a sealing and brake module insertable in said housing to lie adjacent said wiper module; and means cooperating with said housing and said sealing and brake modules to retain said modules in said housing.

References Cited in the file of this patent UNITED STATES PATENTS 2,358,991 

1. IN COMBINATION: A HOUSING HAVING A BOTTOM OF INSULATING MATERIAL WITH SEVERAL ELECTRICALLY CONDUCTING PINS PASSING THERETHROUGH IN HERMETICALLY SEALED RELATION TO PROJECT INWARDLY THEREFROM; A RESILIENT CONTACT MEMBER CARRIED WITHIN SAID HOUSING BY ONE OF SAID PINS; A RESISTANCE WAFER INSERTABLE IN AND REMOVABLE FROM SAID HOUSING INCLUDING AN INSULATING BASE HAVING A FIRST CLEARANCE OPENING FOR SAID ONE OF SAID PINS AND SAID CONTACT MEMBER AND FURTHER CLEARANCE OPENINGS FOR FURTHER PINS, A CIRCULAR RESISTANCE ELEMENT MOUNTED ON SAID BASE, AND SPRING CONTACT MEANS SECURED TO SAID BASE IN ALIGNMENT WITH SAID FURTHER OPENINGS FOR ENGAGEMENT BY SAID FURTHER PINS 